The invention includes embodiments that relate to an electrode composition and method of its making and operation. The invention further includes embodiments that relate to an electrode for an energy storage device.
Metal chloride batteries, especially sodium-nickel chloride batteries with a molten sodium anode and a beta-alumina solid electrolyte, are widely employed for energy storage applications. When the metal chloride batteries are employed in mobile applications, like hybrid locomotives or plug-in electric vehicles (PHEV), or hybrid telecom devices, it is desirable for the batteries to be capable of providing and accepting power during discharging and charging of the battery, respectively. Historically, it has been a focus of battery technology to provide cell compositions that maintain the highest possible operating capacity. In some cell compositions, aluminum has been added, along with other additives, to improve cell performance. However, the amount of aluminum utilized has been minimized, for example to amounts below about 1 weight percent of the positive electrode composition, because amounts in excess of this generally impede operating capacity.
It has now been found that for certain applications, for example hybrid electric vehicles, hybrid telecom devices, and other uninterruptible power systems (UPS) applications, it may be desirable to provide a battery composition that delivers enhanced charge acceptance and cycle life, in conjunction with enhanced discharge power. Modifying the positive electrode composition of a battery may significantly improve the charge acceptance and cycle life, as wells as discharge power, of a battery, even if this is achieved at a reduced cell capacity.
Known battery composition modification mechanisms that have been tried include additives to increase the robustness of the nickel network, additives to promote greater nickel surface area, additives to increase salt availability or surface area, additives to increase use of greater amounts of iron, and the use of added sulfur, in the form of metal sulfides, to increase capacity retention, presumably by poisoning the nickel surface to mitigate against nickel particle growth. Most of these modifications have as their target improved cell capacity.